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Individual study: The use of an ultrasonic deterrent to deter domestic cats Felis catus from entering gardens in the UK

Published source details

Nelson S.H. Evans A.D. & Bradbury R.B. (2006) The efficacy of an ultrasonic cat deterrent. Applied Animal Behaviour Science, 96, 83-91


The impact of domestic cat predation on wildlife populations in the UK is unknown, but many studies show that cats kill large numbers of wild birds and small mammals. In addition, cats are often seen as a nuisance by non-cat owners because of their habits such as defaecation and digging in flower and vegetable beds. For non-cat owners in the UK, deterrent devices offer the only practical solution to keeping cats out of gardens. Various commercial cat deterrents are available from cheap chemical sprays and pellets to more expensive equipment, such as ultrasonic devices. However, there are very few published field experiments of effectiveness of these devices. Field trials was undertaken to test the efficacy of a commercially available ultrasonic deterrent on cats.

Ultrasonic cat deterrent: The deterrent device trialed was a ‘CatwatchTM'. It works by detecting movement and body heat within 12 m, through an angle of 100º. Upon detection, an ultrasonic alarm is triggered operating at a frequency of 21-23 kHz and a volume of 96 db at 1 m, declining to 44 db at 13 m. It is claimed to be effective in scaring cats up to this distance. Earlier trials of a similar device concluded that there was no threat to cat welfare (Mills et al. 2000).

Experimental design: Trials were based on observations by volunteers. Half were given a working device and the other half one that had been disabled. Volunteers were not told which they had been issued with. They were asked to set up the device in accordance to the manufacturers’ instructions i.e. to mount it on the plastic stake supplied or on a wall, so that the heat/motion detector lens was 20 cm above ground level. No advice was given as to where in a garden it should be located. The likely average effect of the device as used by the public (rather than a potentially greater effect that could be achieved through strategic positioning of the device e.g. at entry points regularly used by cats) was therefore tested.

Volunteer throughout the UK were selected to participate if they had an average (100–450 m²) sized, suburban garden, did not already deploy a deterrent and had more than five cat visits to their garden each week. Experiments were carried out over 18 weeks (November 2001-March 2002). Seventy volunteers (63 completing the experiment) were randomly split into one of four groups. Groups 1 and 2 were given a single ultrasonic device to put in their gardens. Group 1 volunteers were given an active device, group 2 volunteers a disabled device. People in groups 3 and 4 were given two ultrasonic devices, one active and one disabled. They were asked to switch the two devices over every month (Table 1, attached, for experimental design).

Probability of a cat intrusion: Average  probabilities of cat presence per week, broken down into the early (weeks 1-9) and late (weeks 10-18) periods of the experiment were 54.2% and 51.5% for disabled devices and 49.9%  reducing to 33.9% for active devices.

Duration of cat intrusions: The interaction between device activity and time was statistically significant. Broken down into early (weeks 1-9) and late (weeks 10-18) periods, duration of intrusions were 0.83 min and 0.95 min for disabled devices, and 0.74 min reducing to 0.46 min for active devices.

Conclusions: Results indicate that the ‘CatwatchTM’ had a moderate deterrent effect, reducing the probability of a cat intrusion into a garden by approximately 32%. The average duration of intrusions was also reduced, by approximately 38%. The magnitude of the deterrent effect appeared to increase with time. It would appear to offer a partial solution to people wishing to deter cats from their gardens. It is possible that the size of the deterrent effect could be increased by positioning the device more carefully with regard to entry points to the garden that are used by cats.

Mills D.S., Bailey S.L. & Thurstans R.E. (2000) Evaluation of the welfare implications and efficacy of an ultrasonic ‘deterrent’ for cats. Veterinary Record, 147, 678-680.

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